Tissue storage of lipids is a principal process in atheroma formation. Light microscopic and electron microscopic studies may help to elucidate the mechanism by which lipid is stored within tissues in various pathological conditions and may provide specific clues to the study of the process of atherogenesis. The differences already noted may help to explain the differences between several different types of atheromata formation. These further electron microscopic studies of cells and tissues from patients with the lipid storage disorders are essentially completed and will be terminated when all samples presently on hand have been examined.